There is shown in FIG. 1 a conventional head drum assembly for use in a digital video cassette recorder including a fixed shaft 1, a drum motor 2, a flange 3, a rotary drum 4, a stationary drum 5, an upper and a lower bearings 6, 6', a first and a second heads 7, 8 and a transformer 10 having a rotor and a stator pieces 11, 13.
The drum motor 2 is adjoined to an upper portion of the fixed shaft 1. The flange 3 on which the rotary drum 4 is fixedly pressed is joined with a middle portion of the fixed shaft 1 via the bearings 6, 6' in such a way that the flange 3 rotates by a driving force of the drum motor 2. The pair of heads 7, 8 are attached on a lower surface of the rotary drum 4. The stationary drum 5 is tightly pressed onto a lower portion of the fixed shaft 1.
The rotor piece 11 of the transformer 10 is attached on the flange 3 and the stator piece 13 thereof is attached on a top surface of the stationary drum 5 in such a way that the rotor and the stator pieces 11, 13 are aligned but separated from each other by a predetermined gap therebetween. Further, the rotor piece 11 is provided with a pair of circular grooves 11a, 11b, wherein the rotor piece groove 11a is used for the first head 7 and the rotor piece groove 11b is used for the second head 8; and also the stator piece 13 has a pair of circular grooves 13a, 13b identical as those of the rotor piece 11, wherein a winding 17 connected to a signal processing system (not shown) is inserted into each of the stator piece grooves 13a, 13b.
Meanwhile, a wire 15 connected to the first head 7 is wound around the rotor piece groove 11a so as to transmit a signal from the first head 7 into the stator piece 13 or vice versa, and another wire 16 connected to the second head 8 is wound around the rotor piece groove 11b so as to transmit a signal from the second head 8 into the stator piece 13 or vice versa.
In such a transformer, at least one rotor piece groove per one head is required, which, in turn, sets a limit on the degree of transformer miniaturization.